


under the sea

by meliapis



Category: Shingeki no Kyojin | Attack on Titan
Genre: Alternate Universe - The Little Mermaid Fusion, F/M, Little Mermaid Elements, Mer!Armin, Mer!Eren, mer!mikasa
Language: English
Status: Completed
Published: 2019-08-18
Updated: 2019-08-18
Packaged: 2020-09-07 00:15:10
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,815
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20300284
Author URL: https://archiveofourown.org/users/meliapis/pseuds/meliapis
Summary: He's almost calmed down when a sound splits through the sea, colors exploding across the surface, casting shadows over him.Curiosity tugs at his very soul.aot mer!au





	under the sea

**Author's Note:**

> a/n: so i found this old boy in the depths of my abandoned google docs and i thought it deserved the light bc it really is a cute idea even if it’s been done a bazillion times with various fandoms. anyway, enjoy!  
warning: old ass writing

“Eren!” A worried voice echoed throughout the dimly lit ship as the wood creaked and groaned beneath the dense depths of the ocean. “We shouldn't be here!”

The frantic quaver in the male’s tone went unheard as a bushel of brown hair popped out and around the bend of a rotten doorway. Tan fingers wrapped around the crusty, wooden frame while wide turquoise eyes blinked, sizing up the rounded room out of sheer curiosity. He hummed at the sight of interesting objects hidden beneath ripped cloths and damaged boards before spotting a few tendrils of hair sinking into his view. Eren glanced up, blowing a lungful of bubbles up to send them scattering back into place. 

Grinning at clear sight he pushes off the door frame, oblivious as dust flies back from his movements. With the help of his glistening tail fin the cloud of filth tumbles right into his companion’s face (who followed behind nervously) leaving him sputtering for clean water. 

While his friend worked with filtering seawater through his gills properly once more, the brunette continued searching around mindlessly. New items were added here and there to his worn satchel as the little light that was left began to fade before brightening once more. The atmosphere was grave as was the illumination. 

“Eren!” 

Said boy rolled his eyes before responding with, “Armin there's nothing to worry about!”

“This is shark territory, there are a plethora of things to worry about!”

“Then just swim back home, guppy,” the explorer snickered. Pursing his lips in wonder, he opened the cracked doors of an old wardrobe, chuckling at the sight of human clothes. He was quick to snatch a hat, the feather atop it fluttering wildly as he adorned it. 

“I'm not a guppy,” Armin muttered, offended. “Besides, Mikasa would kill me if I came home without you.”

“How do I look?” Eren asked, curling his tail like the models back at the kingdom. “Dashing?”

“Outlandish,” the smaller of the duo stated bluntly. “We shouldn't mess with the humans’ things!” He squeaked, wringing his wrists anxiously. 

“I told you there's nothing to worry about. Hmm… Check that desk over there while I see what else is in here,” the brunette replied, upper half burying into the hung up tailcoats and pants. 

“Check the desk. It's not like we're in danger or anything,” his friend mumbles under his breath as he flicks his golden tail to propel him over to the table. “We're just out in the middle of nowhere, finding forbidden objects in a possible shark den. Absolutely nothing to-” his complaining went flat as he leaned over the desk to find a skeleton staring straight up at him, stuck between the chair and desk. 

A shrill scream pierced through the water as he flailed, whipping his lower half forward in terror. Eren could only watch as his partner flew back, narrowly missing him as he shot into the wardrobe. The doors snapped shut with the current created and the brunette howled with laughter, fancy headwear floating off his head as he leaned back, clutching his taut stomach. 

The wooden dresser rattled as Armin whined trapped within, “This isn’t funny. Eren!” 

Shaking his head, the adventurer pulled at the rusted handles and frowned when they didn't budge. Feeling annoyance begin to pool in his stomach the boy set his tail against one door as an anchor while yanking at the other. With a groan of strength the wood snapped, sending him drifting back, wardrobe door in hand. 

He smiled, clutching the handle like it was shield instead of some broken human tool. 

Armin bolted out of the closet, shuddering as he clawed the clothes that had stuck to him off. 

“You're such scaredy fish.”

“I am not!”

As the two friends bickered a shadow wandered over the massive glass window of the captain’s room. The blonde was the one to notice it, turning slowly as the other waved the makeshift shield around playfully. 

“Eren, did you see something just now?” Armin whispered, looking back and forth at the wide panes for any signs of movement. 

“Hmm? No,” the latter answered, careening just in time as a form rounded around the ship. His aquamarine eyes widened in horror as Armin screamed, walloping his tail into action as glass shattered. 

The great white shot across the room towards the brunette, obsidian jaws wide with intent to kill. The boy barely had time to react as he raised the door in his hand, taking the brunt of the attack as he was pushed through the doorway. 

Luckily, the wardrobe piece didn't fit, leaving a blockade for a moment’s escape. 

Eren swam after his friend, satchel dragging at his hip. It wasn't hard to find out where his partner in crime had gone seeing as there was only one exit. That and his screams made an easy trail to follow. 

The telltale crack of breaking wood was their warning to book it as the smarter of the pair slipped through the porthole they'd gone through in the first place to get into the ship. Eren was right on his tailfin, blue-to-green posterior disappearing through the circular window in a heartbeat. 

Their two forms were bright against the dark depths as they fled upwards, but seeing as the brawn of the two had bought them some extra time it was easy to outswim the predator.

One last glance was given over a tan shoulder at the murky distance, the sunken ship fading to black. 

Patting his heavy satchel he smiled to himself, laughing as his companion went into hysterics. 

“Please don't drag me with you ever again! Becoming shark food is not a priority in my life!”

“Please, you'd barely make a meal.”

“Eren!”

The silence had given him false hope upon slipping into his room. He'd assumed his sister was still out and had just managed to return from hiding away his new items when two fingers got a hold of his ear, yanking him out of his security. His white teeth were clearly seen as he gritted them, complaining as he was dragged out of his privacy and into the dining room instead. 

He hit the wall roughly, instantly rubbing his irritated ear as Armin shivered next to him already apologizing, head bowed in grief. 

“He made me do it, I swear!”

“You're such a tattle!” The brunette hissed glaring at the former before a pale hand smacked him across the head. “Son of starfish! That hurts, you know!” He cursed, glaring at his sister. 

“Apparently not enough because you never learn your lesson,” the ravenette replies evenly. 

“You're not my mother!” Eren yells heatedly. 

“No, I'm worse. She'd lecture you. I'm here to beat it into your brain until I see fit to stop. You're not a guppy anymore, Eren, so stop acting like one,” Mikasa scowls, hair coiling around her dangerously. 

“It's not like I'm breaking the rules! We're not allowed to surface--I was nowhere near human territory!” He excused. 

“No, but you're collecting their trash. If the soldiers find out--or worse, the king--you could be severely punished. Humans are forbidden for a reason,” she declares. 

“They'll kill us on sight, Eren. Why do you want to study murderers?” Armin utters. 

“I just think their stuff is cool! Is that such a crime?!”

“Yes!” Both of his roommates hiss. 

“You're ridiculous,” he mutters, crossing his arms as he turns away. 

“We're just trying to protect you,” Mikasa states. “You know better than to go looking for trouble.”

“I don't. It finds me,” the brunette laughs bitterly before diving off his chair. “I'm heading out. Don't wait up for me.”

“Eren!” His sister snaps. 

“Just leave me alone!” He roars before leaving their home in a fit of rage. 

The silence is thick as the blonde sighs, slumping in his seat. All the adrenaline had left his system, taking all of his energy with it. He knew he should have just stayed behind and gotten Mikasa to chase after Eren when he’d asked him to join the outing.

“Adventuring is in his blood. There's nothing we can do about it,” he shrugs, knowing his best friend like the back of his hand. 

“I made a promise,” the female of the trio mutters. “If he gets hurt it'll be on my shoulders.”

“Mikasa…” 

She waves him off. 

“You can head in. I'll wait for him to come back. He just needs to clear his head,” she explains, settling down in a chair. 

Warm hands encase hers. Surprised, her grey eyes look up to meet Armin’s. 

“He'll understand one day,” he assures. When she nods he starts for his room. 

The lights of their small home dim as its third owner swims off into the distance, losing himself in the dark Atlantic waters. 

Besides himself he grumbles under his breath, tail flicking back and forth, agitated. 

He's almost calmed down when a sound splits through the sea, colors exploding across the surface, casting shadows over him. 

Curiosity tugs at his very soul. 

The brunette glances back, seeing his home nowhere in sight. He'd swam farther than he'd thought. 

Sighing, his bright eyes glance up before his tail curls, thrashing against the liquid to send him up. He twirls higher, neck craning to search for any signs of life above the water he called home. All he came make out is blurred, luminous colors. 

As soon as his head breaks the surface another explosion is set off, causing his muscles to tense in fear. Water dribbles from his chocolate tresses, running over his sun kissed skin as his lips part in awe. 

The colors that he saw scatters across the sky. It's like nothing he has ever seen before, leaving him breathless and awed to the core. Voices and cheers echo into the night and the boy turns, blinking at the massive ship sailing yards away. Golden lights surround the wooden structure, beckoning him with its warmth. 

Cautiously he starts for the boat, ducking beneath the water, using its blackness to hide his shimmering scales beneath. 

Catching sight of humans dancing aboard his heart skips excitedly, eyes darting do anything that could get him higher to see. He wanted to observe the strange creatures he'd yet to understand, listen to their peculiar music and study their movements. 

Spotting ridges that made up a ladder on the side of the ship he makes his way over, reaching out of the safety of the sea to grasp the manmade woodcraft. Inhaling a brave breath, Eren begins to ascend, using his strength to bring him higher and higher. His tail is completely useless during the climb, but once he reaches a small opening to see through he settles on a ridge, peering through carefully. 

Human feet pass him by, unknown to the merman aboard. He watches, eyes wide as the creatures before him laugh and step in weird patterns, jostling each other in all good nature. They drink strange concoctions and some words are foreign to his ears. 

It all washes away when he spots her. 

Her laughter is what caught his attention first. It didn't sound like the typical man he saw before him, but feminine and innocent. She's dancing when his eyes find her, dress twirling with her form as she follows the lead of another sailor. 

Crossing his arms to rest his chin he watches, entranced by her beautiful features. She was unlike anything he'd ever seen and it didn't take long for him to fall, face flushing red. 

“Princess! Oh, princess please!” A voice calls from some other spot on the ship. “You should be in bed by now!”

“Oh, hush!” The jewel of his eye speaks and he smiles at her voice. “It's not even late, Sasha!”

“The sun set nearly two hours ago, princess (y/n)!”

(Y/n), he thinks, eyes shutting as he thinks over the name. What a beautiful title for a beautiful girl. 

“Did it? Perhaps I lost track of time!” She laughs, pausing in her dancing to accept a drink offered. Before she can take a sip another female enters the scene, snatching the cup from her hands. 

“A princess doesn't drink!” The presumed Sasha scolds. 

“Lighten up, Sasha! It's a beautiful night! The sea is singing! So dance!” The (h/c)ette giggles, spinning towards the very hole Eren watched through. He gasped, ducking back against the wall as she leaned over the railing. He could hear her take a deep breath and sigh out into the night. 

“The ocean is beautiful! So wild and free! I wish we'd never dock,” she calls and Eren has half a mind to introduce himself. He'd gladly steal her away and show her just what the sea had to offer. She'd live on an island and he'd visit her every waking moment he had…

His daydream fades as the distant sound of thunder echoes. Feeling his scales stand on end the boy frowns. 

A storm is coming and a bad one by the feels of it. 

“Let's return to your cabin. Rain will soon pour,” Sasha says and Eren has just enough time to see her gorgeous face once more before the Lightning hit. 

The heat causes sweat to break over his skin as the wind picks up, spreading the spark that ignited the sail. 

“Oh no,” he whispers before the raging storm begins to pick up. It's all he can do to hang on, but as the sea churns below he's soon thrown off the side, returning to the safety of the water where the thunder and howling wind are muffled. 

His eyes widen at the fierce light of the ship above, burning passed the rippling surface like the sun. Ducking out to see what's happening the sight of smaller boats has him staying low. His heart paces quick in his chest when he doesn't spot his girl of interest. The other female, however, he spots and she’s hollering, clawing at the men who held her back from diving into the angry sea.

Yells are heard and before he can make them out another explosion pierced the air, sending bits of flaming wood flying. The brunette squints, hair flying back at the sudden eruption of heat and a choked gasp leaves him as he spots a figure hit the water. 

Diving into the littered sea he glides through the current easily, searching for the person overboard. His webbed fingers swipe through the salted liquid, eyes frantic to locate her whereabouts. He wasn’t sure how long a human could survive beneath the waves.

He spots a sinking form and instantly scrambles towards her, not caring if she’s awake to see him or not. 

Rules be damned, he wasn’t go to sit there and watch her die. He wasn’t heartless like his cruel ancestors.

Catching her drifting body, he propels to the surface, knowing she needed air for survival. She is unconscious when he finally takes the time to look down at her relaxed face, resting on his bare shoulder. Her skin glistens from the water, hair slick and a few shades darker. 

Watching to see where the boats had fled, he hurries to follow them to shore, battling against wind and rain. 

It’s hours before the furious weather sees the errors of its ways, allowing sunlight to break through the parting clouds

Of course, the merman brings her far away from any wandering eyes, reaching the beach just as the sun peeks over the horizon. 

Sighing, he begins to pushing against the sand, getting her as far on land as he is able. The sun is warm on his skin and it almost causes the girl to glow. Frowning to himself, he lays her on her back, checking for a heartbeat hurriedly. With flushed cheeks he lays his head on her bosom, listening carefully. 

His exhale of relief is loud as he pushed himself to an upright position. 

He can already feel the sand stuck between his scales. It's disgusting. 

Focusing back on his newest treasure, he takes a moment to appreciate the close proximity, hesitantly cupping her face. Her skin is soft, much softer than his and warmer than the sun's rays. It’s sublime holding (many/no) marks that only added to her natural charm.

He can't help but lean over her, eyes flickering to her luscious lips. Leaning down he sighs, eyelids fluttering. She smells of his home and hold a scent that only belongs to the likes of her.

A shouting has him shooting sham-rod straight and searching for the pursuer. Realizing it was time to depart he peers back down at her and sucks in a breath as her eyelids quiver. He just makes out (e/c) irises before he dives back into the sea, returning to deeper waters where no one could see him for what he was. 


End file.
